Our proposed studies are directed toward obtaining a better understanding of the mechanisms of infection of implanted cardiovascular biomaterials. Our hypothesis is that material surface interactions with flowing blood lead to alteration of basic pathophysiologic mechanisms that increase the probability of bacterial interaction and infection. The studies emphasize the use of clinically derived human materials, i.e., blood and bacteria, and clinically relevant cardiovascular materials coupled with controlled in vitro systems to systematically and comprehensively elucidate infection mechanisms with cardiovascular biomaterials. The overall goals of the project are to: 1) understand how blood protein adsorption and shear stress mediate genotypic and phenotypic aspects of initial Staphylococcus epidermidis adhesion and biofilm formation, 2) examine the role of biomaterial surface chemistry of clinically relevant and model cardiovascular biomaterials in modulating genotypic and phenotypic aspects of biofilm formation, 3) evaluate the bactericidal capacity of leukocytes in the presence of a Staphylococcus epidermidis biofilm formed on cardiovascular biomaterials, 4) develop a treatment for infection by using the fibrinogen-Fbe binding mechanism by which Staphylococcus epidermidis specifically adheres to thrombus formations on cardiovascular biomaterials, and 5) utilize an in vivo biomaterial infection model in rabbits for in vivo-in vitro correlations. Genotypic variations in S. epidermidis adhesion and biofilm will focus on identifying changes in gene expression of the Atle autolysin, capsular polysaccharide adhesin, polysaccharide intercellular adhesin, accumulation associated protein and accessory gene regulator. Corresponding phenotypic studies will quantify S. epidermidis adhesion, aggregation and viability, as well as slime production and biofilm thickness on the various cardiovascular biomaterials. Leukocyte bactericidal capacity in the presence of biofilm on biomaterials will be characterized by leukocyte adhesion, chemotaxis, reactive oxygen and nitrogen species production, phagocytosis, and apoptosis. A fibrinogen-based peptide sequence based on fibrinogen/Fbe (S. epidermidis) will be used as a blocking ligand to investigate adhesion blocking mechanisms to prevent bacterial aggregation and biofilm formation.